Two rotary motors in FoF1-ATP synthase convert electrochemical energy via a mechanical form of energy to chemical energy. In the Fo portion proton transport across the membrane causes rotation of a ring of 10 c-subunits with respect to the non-rotating a- und b-subunits ( Fo motor ).
The g- and e-subunits of the F1 portion are connected to the c-ring and thus are forced to rotate within the a3b3 hexamer. The stepwise rotation of the g-subunit induces conformational changes in the b-subunits, which leads to synthesis and release of ATP. According to their ADP and ATP binding affinities three different conformational states of the b-subunits are distinguished. The relative g-subunit position determines the actual state of each b-subunit. Turning the g-subunit in the catalytic cycle initiates cooperative sequential conformational changes in the b-subunits ( F1 motor ).